1. Field of the Invention
This invention relates to a process for manufacturing a body of an iron-nickel alloy having a complicated shape and exhibiting a high level of soft ferromagnetic properties.
2. Description of the Prior Art
Pure iron is a soft ferromagnetic material exhibiting a high saturation magnetic flux density and is widely used as a material for yokes in pulse motors, relays, printer heads, etc. Precision casting has been employed for making a part of pure iron. It has, however, been likely that a defective casting may be made, as the desired dimensional accuracy of sharp edges or points is difficult to obtain. Attempts have, therefore, been made to employ powder metallurgy for making, among others, parts having complicated shapes.
It is, however, impossible to make a product of pure iron having a complicated three-dimensional shape by any ordinary method of powder metallurgy relying upon compression molding. As it is necessary from a compressibility standpoint to use a relatively coarse powder having an average particle diameter of, say, 100 microns, and as pure iron is not easily diffusible, it is difficult to a product having a sintered density which is sufficiently high to realize the desired magnetic properties. It is necessary to compress and sinter a sintered product again to increase its density, or it is necessary to rely upon prolonged sintering, or hot isotactic pressing (HIP). If it is necessary to give a sintered product a dimensional finish by machining, it is necessary to heat treat it thereafter to relieve it of any resulting stress.